In the past, many downhole tools, such as bridge plugs or packers, have been used that are settable hydraulically. In some applications, the downhole tool is positioned in the wellbore with a wireline. Attached to the wireline assembly is a downhole pump which takes suction within the wellbore and builds the pressure up into the downhole tool for its actuation. Typically, these downhole pumps are driven by downhole motors are supplied with electrical power from the wireline and are limited in their pressure output to output pressures in the order of up to about 3,000 psig. Lately, the technology in downhole tools, particularly bridge plugs and packers, has evolved where higher setting pressures are required to assure the sealing integrity of the packer or plug. This is particularly true in environments where larger differential pressures are expected and the sealing force must be enhanced to a sufficient level to withstand the expected differentials across the plug or packer.
In the past, the physical configuration of the downhole pumps, as well as the logistics of supplying sufficient power to operate downhole motors, has been a limiting factor in the ability to apply setting pressure to bridge plugs or packers and similar hydraulically settable downhole tools. One solution to the space problem in the wellbore has been to stack a plurality of pistons in parallel so that the available setting pressure acts simultaneously on all the pistons. However, these devices did not magnify the applied pressure and, hence, the applied pressure available for setting the downhole tool.
Accordingly, it is an objective of the present invention to provide a simple device which can be readily used in conjunction with the pressure developing pump or a similar device used to create the motive force to set the downhole tool. It can also be used when the tool is run on tubing and a boost force is needed. The boosting device operates automatically and is simple to construct and effective to get a predetermined ratio of increase in applied force to set a downhole tool.